Electronic timing device



Oct. 15;.i946. E. M. CALLENDER ELECTRONIC TIMING DEVICE Filed Jan. 4, 1944 JNVENTOR L' dwin M Callendez;

ggy Y [6 ATTO NEY Patented Oct. 15, 1946 ELECTRONIC TIMING DEVICE.

Edwin M. Callender, Philadelphia, Pa., assignor to The Budd Company, Philadelphia, Pa., a corporation of Pennsylvania Application January 4, 1944, Serial No. 516,928

11 Claims.

This invention relates to an electronic timing device of the type having adaption for indicating a repeated cycle of operation.

In many industrial operations and in the utilization of various equipment in the arts, such as photographic apparatus, it is frequently desirable that the apparatus function intermittently at a uniform time interval with a uniform maintenance of effectiveness at each interval. For example, in aircraft photography where it is desirable to secure landscape photographs at definite time intervals there being a predetermined length of exposure at each interval, apparatus of the above-described type is essential.

It is one of the important objects of the invention to provide a timing device of the electronic type which functions with complete uniformity as to time for length of actual interval and for time period between intervals, provided a constant source of voltage is impressed on the unit. Another important object of the invention is to provide apparatus of the type mentioned in which adjustability to on or off position may separately be accomplished and with a close degree of gradation of time.

In the following specification there is described v apparatus which may be preferred for accomplishing the objects hereinabove mentioned, the elements of the circuit being diagrammatically indicated in the accompanying drawing. With special reference to the drawing I have indicated terminals l0 and H which are adapted for connection to a source of alternating current. Connected to these terminals are the conductors l2 and I3 hereinafter referred to as mains or lines between which the timing apparatus is connected. Two load circuits, referred to in the claims as first and second loads, are indicated in the diagram, one from the point l4 through load l5, relay contact l6, relay arm 21 and conductor I! to the opposite main l3, and the other circuit from point [4 to load I8 through relay contact [9, arm2l, to circuit I1 and power main I3. Each of these loads may consist of an indicating element such as a lamp which when the current flows therethrough is energized.

The relay 2!] for making effective current flow through the contacts l6 and 19 of the load circuits comprises a coil 2| having a magnet core 22 and movable armature 23 fixed to a contact member 24 including a central insulation block 25 and spaced contact plates 26 and 21 extending on either side from the insulation block 25 and pivoted at point 60. The arm 21 is positioned between the contacts l6 and IQ of the load circuit,

and, in the de-energized position of the relay, rests on the lower contact l9 by gravity, or equivalent means thus completing the circuit through the load 18. When, however, the relay is energized, the arm 2! moves upwardly and engages the upper contact l6 thereupon breaking the circuit through [8 and closing it through the load It. In the description that follows, load I8 is referred to as an o load and load l5 as an on load, visualize a lamp as load [5 and a non-luminous resistor as load I 8.

The lower end of the coil 20 is extended downwardly and connected with the anode 30 of a grid-controlled-gaseous-discharge tube, otherwise known as a thyratron. This tube encloses a shield grid 32 and control grid 33, an indirectly heated cathode 34 and a heater filament 35. The main I3 is directly connected to the cathode of this tube.

'As is well known, a tube of the mentioned type passes current only in one direction, namely, from the anode to the cathode and the starting of this current how when the appropriate voltage exists between the tube elements is controlled by the various grids of the tube, a negative potential on the control and shield grid of sufficient value preventing the flow of current between the anode and cathode and a decrease of this negative potential on the other hand to a point approaching zero permitting the current to again flow between the tube elements. In the operation of the circuit a zero or slightly negative potential on the grids 32 and 33 with a line potential of or more volts on the mains permits current flow through the relay circuit and thyratron 3|.

The gas filled diode tube 36 is associated with the thyratron 3| in perfecting the time control of the apparatus. The anode 31 of the diode is connected to the upper contact 38 associated with the armature plate 26 of the relay and is normally disconnected therefrom as shown. The cathode 39 of the diode is extended from the tube to one end 40 of the variable resistor 4| having a slidable contact 42 for obtaining a fine gradation of resistance and variation. Connected to the other terminal 43 of the variable resistor is a fixed resistor 44 having a resistor terminal 45, one of a bank of resistor terminals 45, 46, 41 and 48, each of which may be connected to the power main l2 by means of a movable contact arm 49. Terminal 46 is connected through fixed resistor 50 and terminal 41 through fixed resistor 5| in Parallel to the terminal 45. The terminal 48 is connected through a fixed resistor 52-to one end 40 of the variable resistor 4|. The values of these resistors are adjusted so as to give a broad variation in total resistance between the diode cathode 33 and the power main 12. For example, in the specific circuit described, to give excellent results the values of the resistor 4| should be .5 megohm, resistor 44, 15 thousand ohms, resistor 50, megohm, resistor 5|, 3 megohms and resistor 52, 10 megohms. All of these resistors, it is pointed out are included in the on load circuit and are effective in adjusting the time interval during which the relay is energized and load I5 is receiving current.

The diode 36 is provided with a heater 53 for the cathode 39, this heater having a series connection with the heater of the thyratron 3|, the current for these heater filaments being supplied from the secondary 54 of the transformer 55, the primary 56 of which is connected directly across the mains. To insure a proper functioning of the tubes 3| and 36, switches 51 and 58 are placed in the main l2 on either side of the point I4 to include the connection to the transformer 56 so that power may be applied to the transformer with the switch 58 open to delay activation of the relay. Screen grid 32 of the thyratron 3| is connected through a leakage resistor 59 to the end 60 of the armature plate 26 and from this point a conductor Bl connects to a bank of capacitors 62 and 63, a switch 64 providing means for adjusting the capacitors of the capacitor bank. Conductors 35 and 66 connect the capacitors to the power main 13. The transient arresting capacitors 61 and 35 are connected between the cathode 3d of the thyratron and screen grid 32 and control grid respectively.

Control grid 33 is connected through a resistor 68 to the lower contact 69 adjacent relay armature 25. This grid is also connected through the grid resistor 68 to a resistance arm 13) making positive contact with the resistor terminal H, l2, l3 and M. Terminals 12, T3 and I4 connect respectively with resistors 15, i6 and 11, the same forming a parallel circuit to a conductor "(8 in conjunction with the conductor 19 from the terminal ll The conductor 18 leads through th variable resistor 86 having a movable contact arm 8| and through the fixed resistor 82 to the main 13. For the specific arrangement hereinabove referred to, values for these resistors found satisfactory are resistor '15, 5 megohms, l6, l0 megohms, T1, 20 megohms, resistor 80, 400,000 ohms and resistor 82, 1 /2 megohms.

In addition to the resistor lit. connected directly to the control grid of the thyratron, use is made of a leakage resistor 33 which in the circuit as set up with the control resistor as indicated may have a value of 10 megohms. This value assisted with the value of 10 megohms for the resistor 68 affords a satisfactory leakag path for the capacitors as will now be explained.

In the operation of the apparatus, switch 5"! is closed, thereby energizing the transformer 55 and causing filaments 35 and 53 of the tubes to become heated. With the proper load elements in the load circuits for the on and off positions, the switch 58 is closed thereby impressing on the anode of the thyratron 3| a. potential of sufficient value, in view of the zero potential of the grids, to cause a flow of current through the tube during the positive alternation of the initial cycle of current alternation. This flow of current energizes the relay 20 which lifts armature 23, closing the on load circuits l5 and I6 and the circuit from the diode anode 31 to the screen grid 32 of the thyratron.

On the reversal of the line voltage the relay armature remains in the closed position. This is made possible through the use of a so-called telephone type relay which employs a shading ring on the movable armature end, the action of which is to make effective the pull of the armature through the negative half cycle. This arises from the fact that the current and flux values of the relay coil and the shaded ring are out of phase with each other, the shaded ring voltage being out of phase with the primary potential so that the simultaneous eiiect of coil and shading ring values is to extend a positive pull of flux over substantially all of the negative half cycle of the line voltage and this extension coinbines with the physical lag of the armature to maintain the armature of the relay in closed position througi'iout the period of alternation. (For definition of shaded coil see page 489, Stand ard Handbook for Electrical Engineers, 7th edition, 1941.)

On the reversal of the voltage in the power mains, after the first positive half .cycle, current is interrupted through the thyratron and is permitted to how into and charge the condensers 62 and the circuit being completed through the point contact 38, diode anode 3i and cathode 39 and through the on resistor control to the main 12. The amount of current flow is, of course, controlled by the adjustment of the resister arms c2 and 40 in the on unit, larger resistance decreasing the amount of current flow. in this negative half cycle of current flow a definite limited quantity of current is passed into ti-re capacitors $52 and 63 which is at once efieotive as a negative potential on the screen grid 32 thus cing the potential of the grid below zero. At t e second positive half cycle current again passes through the thyratron 3i re-energizing the relay 2:3 and on the second negative half cycle a further increment of charge is efiected in the capacitors thus reducing by a second definite amount the potential of the screen grid 32. Subsequent alternations oi" the cycle build up the negative charge on the screen grid 32 to the point where it falls below the striking potential of the tube, at which point current will fail to flow through the thyratron at the next positive half cycle and the on position of the circuit will thus be ended. At the moment of break of current through the thyratron due to the action of the shield grid 3'2, the relay 20 becomes de-energized and the armature falls thus breaking contact with the on load 15 and making contact with the off load is and simultaneously making contact between the capacitors and the off control resistor unit arm 10. It will be seen that placement of the resistor arm H0 at any given resistor terminal will result in a leakage flow of current from the capacitors 62 and 63 which, after a predetermined time interval as determined by the particular resistor to which the arm '10 is connected, reduces the negative potential of screen grid 32 to a point where it will exceed the striking potential of the tube whereupon current will once again flow through the thyratron in the positive half cycle of the line voltage and charging of the capacitor 82 will again be resumed.

It is pointed out in connection with the thyratron that as the load passes from on to off position and the relay 2!! is de-energized a connection is made between capacitor 612 or 63 and the control grid 33 whereby the negative biasing oi" the shield grid is amplified. This is due to the fact that the control grid is closer tothe cathode than the screen grid and therefore a reversal of effect at the critical striking point is prevented through the joint action of both screen and control grids.

As described, the off position of the load circuit is confined to the time period in which the leakage current flows through the oif control unit to the point of reversal. The leakage effect is supplemented also by the resistors 68 and 83 connected to the control grid to form a circuit to the power main I3.

The circuit as described including the electronic elements and accessory relay and other apparatus has been found eficient and particularly applicable to the purpose and effective in accomplishing the objects of the invention. However, modifications of the circuit and elements may, of course, be made to accommodate the same to particular uses, and hence, no limitation is implied by the specification other than indicated by the claims as hereto appended.

What is claimed is:

1. An electric timing device comprising power mains, a normally closed first load circuit, a normally open second load circuit, relay means for connecting alternately said first and second load circuits to the power mains, and time change means for independently adjusting the timing of said alternate load circuit connection both as to off and on positions.

2. An electronic timing device comprising power mains, a normally closed first load circuit, a normally open second load circuit, relay means for connecting alternately said load circuits to the power mains, and time change means for adjusting the timing of said alternate load circuit connections, said relay means comprising a relay, load circuit switch contacts operable by said relay, an electronic device including a control grid, a branch circuit conductor connecting said relay and electronic device in series across said mains, and a capacitor connected to said control grid and to said mains adapted to impress at recurrent intervals a negative potential on said grid of sufficient value to disrupt the current flow in said electronic device and relay.

3. An electronic timing device comprising power mains, a normally closed first load circuit, a normally open second load circuit, relay means for connecting alternately said load circuits to the power mains, and time change means for adjusting the time of said alternate load circuit connections, said relay means comprising a, relay, load circuit switch contacts operable by said relay, an electronic device including a control grid, a branch circuit conductor connecting said relay and electronic device in series across said means, a capacitor connected to said control grid and to said mains adapted to impress at recurrent intervals 2. negative potential on said grid of sufiicient value to disrupt the current flow in said electronic device and relay, and means for varying the length of said intervals.

4. An electronic timing device comprising power mains, a normally closed first load circuit, a normally open second load circuit, relay means for connecting alternately said load circuits to the power mains, and time change means for adjusting the timing of said alternate load circuit connections, said relay means comprising a relay, load circuit switch contacts operable by said relay, an electronic device including a control grid, a branch circuit conductor connecting said relay and electronic device in series across said mains, a capacitor connected to said control grid and to said mains adapted to impress at recur- ,rent'intervals a negative potential on said grid of sufiicient value to disrupt the current flow in said electronic device and relay, and means to reduce said negative potential to a point where current flow is resumed through said electronic device.

5. An electronic timing device comprising power mains, a normally closed first load circuit, a normally open second load circuit, relay means for connecting alternately said load circuit to the power mains, and time change means for adjusting the timing of said alternate load circuit connections, said relay means comprising a relay, load circuit switch contacts operable by said relay, an electronic device including a control grid, a branch circuit conductor connecting said relay and electronic device in series across said mains, a capacitor connected to said control grid and to said means adapted to impress at recurrent intervals a negative potential on said grid of sufiicient value to disrupt the current flow in said electronic device and relay, means to reduce said negative potential to a point where current fiow is resumed through said electronic device, and said time change means including plural means for controlling the time intervals in which current does, and does not, iiow.

6. An electric timing device comprising power mains, first and second load circuits connected to said mains, relay means including switch mechanism in said load circuits for transmitting power from said mains alternately through each of said load circuits through movement of said switch mechanism and timing means for fixing the time of alternation of said relay switch mechanism, said relay means including a coil magnet, an armature associated therewith and connected to said switch mechanism to bring about alternate load circuit contacts, and means connected to said magnet for permitting current flow therethrough in one direction only.

'7. An electric timing device comprising power mains, load circuits connected thereto, switch mechanism operative to connect alternately each load circuit to said mains, a relay circuit including a relay operative to move said switch mechanism to secure alternate connection of said load circuits, means in said relay circuit for transmitting current therethrough in one direction only, and timing means for fixing the period of current flow and non-flow in said relay.

8. An electronic timing device comprising power mains, plural load circuits, switch mechanism for connecting each load circuit alternately to said mains, relay means connected to said mains for actuating said mechanism, an electronic device connected to said relay means for passing current through said relay means in one direction only, said electronic device including a control element, and means connected to said control element for interrupting periodically the flow of current through said relay means.

9. An electronic timing device comprising power mains, dual load circuits, and relay means for connecting said load circuits alternately across said mains, said relay means comprising a relay, load circuit switch contacts operable by said relay, an

electronic device including a control grid, a

branch circuit conductor connecting said relay and electronic device across said mains, and means connected to said electronic device for recurrently blocking current flow therethrough.

10. An electronic timing device comprising power mains, dual load circuits, relay means for connecting said load circuits alternately across said mains, and time change means for adjusting the timing of said alternate load circuit connections, said relay means comprising a relay, load circuit switch contacts operable by said relay, an electronic device including a control grid, a branch circuit conductor connecting said relay and electronic device across said mains, and means connected to said electronic device for recurrently blocking current flow therethrough.

EDWIN M. CALLENDER. 

